1. Field of the Invention
This invention relates to a thermal fuse which can be assembled automatically and works accurately.
2. Description of the Prior Art
Conventionally, a thermal fuse is connected to a circuit as a safety means for various electric appliances and electric circuits. This conventional thermal fuse is so designed that when a preset temperature is reached, fusible alloy which constitutes a part of the electric circuit fuses and opens the electric circuit, thereby protecting electric appliances and preventing a fire. In this thermal fuse, two lead wires arranged oppositely or in parallel with each other are brought compulsorily into contact with each other to close the electric circuit between the two lead wires and a contact part is deposited with fusible alloy which is adapted to fuse at the preset temperature. Therefore, when the temperature of the electric circuit itself reaches the preset temperature due to the flow or impression of more electric current or voltage than present in the electric circuit, with resultant overload on the electric circuit, or when the ambient temperature is higher than the preset temperature, the fusible alloy connecting the two lead wires and closing the electric circuit fuses and opens the electric circuit.
In the above conventional thermal fuse, an electrode wire bridges two lead wires and an intersecting point of each lead wire, and the electrode wire is deposited with fusible alloy so as to close an electric circuit between the two lead wires. Therefore, two deposition portions are provided and it is necessary to provide a means for preventing the electrode wire from contacting again after the fusible alloy fused and the electrode wire was separated from the lead wires, namely, the electric circuit was opened.
In assembling the conventional thermal fuse, lead wires are deposited directly with fusible alloy and therefore full automation of the assembling process is difficult to realize and it requires much trouble to assemble the thermal fuse, especially in the case of a thermal fuse of super small-size.
In the case where depositing of the electrode rod is effected while two lead wires are compressed by springs, such compression must be maintained until the fusible alloy hardens.